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But whence the week? Throughout history, human societies have found it useful to divide time into groups of days shorter than a lunar month. One of the most common uses of this cycle has been to establish a regular market day, though just how regular varies. At one point, the Basques evidently employed a three-day week. For centuries, China, Japan, and Korea employed a 10-day week. Other societies have employed four-, five-, six-, eight-, and nine-day weeks.

So how did lucky No. 7 come to rule our calendars? It all began logically enough, when the ancient Babylonians divided their lunar months into four, yielding weeks that were mostly seven days. Then superstition kicked in. The final day of the week came to be considered evil or unlucky, and certain taboos developed around that day—against eating meat, for example.

It’s likely that the Babylonian week was the model for the seven-day Jewish week, with its own taboos against certain behaviors on the seventh day, or Sabbath. Babylon also probably served as the source of another important seven-day week used in Hellenistic Alexandria. The influence of that week remains with us in the names of heavenly bodies it assigned to each day—like Saturn-day, Sun-day, and Moon-day.

Meanwhile, the Romans marked time differently, which is why you never heard of anyone warning Caesar to “beware the third Tuesday in March!” Roman lunar months began on the Kalends, which scholars believe coincided with the new moon. The Ides, which fell on the 13th or 15th day of a month, coincided with the full moon. The Romans also kept an eight-day market week.

As Christianity—which kept the Jewish week but moved the Sabbath to Sunday—and Egyptian astrology gained influence in the empire, so did the seven-day week. Constantine, the first Christian emperor, made it official in 321. Since then, the spread of Christianity’s influence—as well as that of Islam, which also employs a seven-day week—has imposed the seven-day cycle on most of the world.

But there’s nothing inevitable about the ceaseless repetition of six days of work, one day of rest. As labor has become both more productive and more organized, the week has evolved. The writer Witold Rybczynski traces the emergence of the weekend to 19th century England, when the British agricultural revolution made land and labor more productive. At first, Rybczynski relates, this allowed workers extra leisure, which they enjoyed spontaneously—not according to any ironclad schedule. As the Industrial Revolution became a driving force in trans-Atlantic civilization, the push for greater efficiency demanded standardization of this extra leisure. In 1926, Henry Ford began shutting his factories on Saturdays in a bid to crystallize an American convention of a two-day weekend full of recreation (that he hoped would involve driving). It worked.

http://www.slate.com/articles/life/culturebox/2014/05/abolish_the_week_the_case_against_dividing_time_into_seven_day_periods.single.html
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After Centuries of Lost Ideas, Humans Saved History by Sending It to Space   

By far the most tantalizing loss from the library [of Alexandria] was a treatise by the mathematician Aristarchus of Samos (310–230 BCE) that provided the first model for a heliocentric universe. That’s right: this guy casually figured out that the Earth was orbiting the Sun some 2,300 years ago, and we have no real idea how he did it.

His argument was destroyed along with the rest of the Library, but we know that it existed because Archimedes wrote the following passage about it in The Sand Reckoner.

It is gut-wrenching to think that the true nature of the solar system had been successfully divined all the way back in the third century BCE, only to be suppressed for another 1,800 years.

Imagine how different the course of history might have been had this revolutionary idea been fostered and investigated instead of ridiculed, dismissed, and ultimately engulfed in flames. For better or for worse, we would have been a very different species if Aristarchus’ contemporaries had embraced his findings instead of accusing him of impiety.

After Centuries of Lost Ideas, Humans Saved History by Sending It to Space   

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So why don’t we see advanced civilizations swarming across the Universe? One problem may be climate change. It is not that advanced civilizations always destroy themselves by over-heating their biospheres (although that is a possibility). Instead, because stars become brighter as they age, most planets with an initially life-friendly climate will become uninhabitably hot long before intelligent life emerges.

The Earth has had four billion years of good weather despite our Sun burning a lot more fuel than when Earth was formed. We can estimate the amount of warming this should have produced thanks to the scientific effort to predict the consequences of man-made greenhouse-gas emissions.

These models predict that our planet should warm by a few degrees centigrade for each percentage increase in heating at Earth’s surface. This is roughly the increased heating produced by carbon dioxide at the levels expected for the end of the 21st century. (Incidentally, that is where the IPCC prediction of global warming of around three degrees Celsius comes from.)

Over the past half-billion years, a time period for which we have reasonable records of Earth’s climate, the Sun’s surface temperature increased by four percent, and terrestrial temperatures should have risen by roughly 10 degrees Celsius. But the geological record shows that, if anything, on average temperatures fell.

Simple extrapolations show that over the whole history of life, temperatures should have risen by almost 100 degrees Celsius. If that were true, early life must have emerged upon a completely frozen planet. Yet, the young Earth had liquid water on its surface. So what’s going on?

The answer is that it’s not only the Sun that has changed. The Earth also evolved, with the appearance of land plants around 400 million years ago changing atmospheric composition and the amount of heat Earth reflects back into space. There has also been geological change with the continental area steadily growing through time as volcanic activity added to the land-mass. This too had an effect on the atmosphere and Earth’s reflectivity.

Remarkably, biological and geological evolution have generally produced cooling, and this has compensated for the warming effect of our aging Sun. There have been times when compensation was too slow or too fast, and the Earth warmed or cooled, but not once since life first emerged has liquid water completely disappeared from the surface.

Our planet has therefore miraculously moderated climate change for four billion years. This observation led to the development of the Gaia hypothesis that a complex biosphere automatically regulates the environment in its own interests. However, Gaia lacks a credible mechanism and has probably confused cause and effect: a reasonably stable environment is a precondition for a complex biosphere, not the other way around.

Other inhabited planets in the Universe must also have found ways to prevent global warming. Watery worlds suitable for life will have climates that, like the Earth, are highly sensitive to changing circumstances. The repeated canceling of star-induced warming by “geobiological” cooling, required to keep such planets habitable, will have needed many coincidences, and the vast majority of such planets will have run out of luck long before sentient beings evolved.

http://arstechnica.com/science/2014/06/why-havent-we-encountered-aliens-yet-the-answer-could-be-climate-change/ (via fuckyeahdarkextropian)

A solar system full of dead worlds and moons.

Dried up sea beds of underground oceans rich in the fossils of life that lasted just a while. And the ones that made it in their own unique way.

Let’s go see.

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Cracks in Pluto’s Moon Could Indicate it Once Had an Underground Ocean

In Charon’s case, this study finds that a past high eccentricity could have generated large tides, causing friction and surface fractures. The moon is unusually massive compared to its planet, about one-eighth of Pluto’s mass, a solar system record. It is thought to have formed much closer to Pluto, after a giant impact ejected material off the planet’s surface. The material went into orbit around Pluto and coalesced under its own gravity to form Charon and several smaller moons.
 
Initially, there would have been strong tides on both worlds as gravity between Pluto and Charon caused their surfaces to bulge toward each other, generating friction in their interiors. This friction would have also caused the tides to slightly lag behind their orbital positions. The lag would act like a brake on Pluto, causing its rotation to slow while transferring that rotational energy to Charon, making it speed up and move farther away from Pluto.

“Depending on exactly how Charon’s orbit evolved, particularly if it went through a high-eccentricity phase, there may have been enough heat from tidal deformation to maintain liquid water beneath the surface of Charon for some time,” said Rhoden.
“Using plausible interior structure models that include an ocean, we found it wouldn’t have taken much eccentricity (less than 0.01) to generate surface fractures like we are seeing on Europa.”

“Since it’s so easy to get fractures, if we get to Charon and there are none, it puts a very strong constraint on how high the eccentricity could have been and how warm the interior ever could have been,” adds Rhoden. “This research gives us a head start on the New Horizons arrival – what should we look for and what can we learn from it. We’re going to Pluto and Pluto is fascinating, but Charon is also going to be fascinating.”

Based on observations from telescopes, Charon’s orbit is now in a stable end state: a circular orbit with the rotation of both Pluto and Charon slowed to the point where they always show the same side to each other. Its current orbit is not expected to generate significant tides, so any ancient underground ocean may be frozen by now, according to Rhoden.

Cracks in Pluto’s Moon Could Indicate it Once Had an Underground Ocean

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Massive ‘ocean’ discovered towards Earth’s core

The water is hidden inside a blue rock called ringwoodite that lies 700 kilometres underground in the mantle, the layer of hot rock between Earth’s surface and its core.

The huge size of the reservoir throws new light on the origin of Earth’s water. Some geologists think water arrived in comets as they struck the planet, but the new discovery supports an alternative idea that the oceans gradually oozed out of the interior of the early Earth.

“It’s good evidence the Earth’s water came from within,” says Steven Jacobsen of Northwestern University in Evanston, Illinois. The hidden water could also act as a buffer for the oceans on the surface, explaining why they have stayed the same size for millions of years.

Massive ‘ocean’ discovered towards Earth’s core

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